Cable pullers are used by electrical contractors to pull cables through pipe or conduit so that the cables can be terminated at either end. Once terminated, these cables can be used to supply power or data between locations. In particular, cables that supply power can require significant forces in order to be pulled. For this reason, cable pullers are used that typically comprise a motor that powers a drive sprocket, which then transmits torque to a capstan around which a pulling rope can be wound. It is often the case that a drive chain is the means used to connect the capstan to the drive sprocket so that the torque from the motor can be transmitted to the capstan. The capstan is configured to rotate in a primary direction during which the pulling rope is wrapped around the capstan, causing the wire or cable to be pulled through the conduit.
In use, the pulling rope is fished through the conduit by means commonly known in the art after it has been attached to the cable that is to be pulled. Once the cable puller is turned on, the motor causes the drive sprocket to rotate, which transmits its torque to another sprocket to which the capstan is connected by the drive chain. As the capstan begins to rotate, the pulling rope is wound around it such that the user can pull onto its tail end. This arrangement creates a great amount of mechanical advantage, aiding in pulling the cable through the conduit. During a cable pull, great amounts of force in the order of magnitude of thousands of pounds can be exerted on the components of the cable puller. Consequently, these parts can become stressed and can be damaged or broken, including the drive chain. If the drive chain should break, it is very undesirable that the capstan should rotate in a direction that is opposite to the primary direction for a host of reasons including safety.
For this reason, an anti-reversing pawl is often employed such that if the capstan should rotate in the wrong direction, the pawl will engage the capstan and stop it from moving. Pawl mechanisms that have been previously employed are needlessly complex and require too much time to assemble, making them costly. In addition, they often continuously engage the teeth that are part of the sprocket that drives the capstan, which is an ineffective method for pulling rope when the capstan is operating at high speeds because of the drag it creates on the sprocket. Another drawback of this design is that it creates a significant amount of noise as the pawl engages each individual tooth of the sprocket. Yet another drawback is that there is wear on the part of the pawl that engages the sprocket, which could adversely affect the manner in which the pawl engages the sprocket when it needs to prevent the capstan from reversing its direction. Accordingly, there exists a need for an anti-reversing pawl mechanism that is simpler, cheaper, quieter, more robust, and that will work effectively at high speeds without creating unnecessary drag.